1. Field of the Invention
The present invention relates to an apparatus and a method for controlling writing data, and more particularly, relates to an apparatus and a method for controlling writing data to a tape medium.
2. Description of the Related Art
There is a system which is equipped with tape media such as magnetic tapes and repeats writing and reading operations of relatively small amounts of data to and from each tape medium (for example, see Felix Ehm, “Development of a Performant Defragmentation Process for a Robotic Tape Library within the CASTOR HSM,” (online), 2006, (searched on Dec. 9, 2009), the Internet URL:http://castor.web.cern.ch/castor/docs/guides/DiplomaThesis.pdf (“Ehm”), Tim Bell, “Tape Efficiency Version 0.5,” (online), November 2007, (searched on Dec. 9, 2009), the Internet, URL:https://twiki.cern.ch/twiki/pub/FIOgroup/TapeRefCernUsageNov2007/tape_usage_efficiency_v05.pdf (“Bell”), and C. Curran, “The Unbearable Slowness of Tape,” (online), May 2008, (searched on Dec. 12, 2009), the Internet <URL:http://hepix.caspur.it/storage/hep_pdf/2008/Spring/hepix8.pdf>(“Curran”)). Since a tape medium is a removable recording medium, writing or reading data requires the tape medium to be loaded on a tape drive. In addition, since the tape medium is a sequentially accessed recording medium, writing or reading data also requires a head for writing or reading to be moved to a writing position or a reading position on the tape medium. Thus, in general, such a system repeatedly performs operations such as moving a tape cartridge from a storage place to a tape drive (Move Medium), loading the tape cartridge on the tape drive (Load), moving a head of the tape drive to a writing or reading start position (Locate/Space), writing or reading data (Write/Read), rewinding the tape medium (Rewind/Unload), unloading the tape cartridge from the tape drive (Unload) and moving the tape cartridge to the storage place (Move Medium).
Generally, times required for the above operations are: several tens of seconds to move the tape cartridge from the storage place to the tape drive and to load the tape cartridge on the tape drive; several tens of seconds on average to move the tape medium of the tape cartridge to a writing or reading start position and to rewind the tape medium; and several tens of seconds to unload the tape cartridge from the tape drive and to move the tape cartridge to the storage place. These operations thus requiring a total of several minutes are an overhead of data writing or reading which can be completed in several seconds. In this sense, it can be said that the tape medium is used in an unsuitable manner in the system described in Ehm, Bell, and Curran mentioned previously.